In a waterproof microphone generally used, often, an acoustic terminal unit is covered with a waterproof film, for example, such as a plastic film, rubber, etc., on the supposition that a user erroneously drops it into water.
In this waterproof film is set to an appropriate shape and thickness so that it is not broken even if a fixed water pressure exerts thereto and returned to its original shape.
In the thus set waterproof microphone, a sound wave having passed transmitted the waterproof film arrives at the acoustic terminal unit.
Accordingly, for enhancing various properties such as the sensitivity, frequency responsiveness, etc. of the waterproof microphone, it is necessary to make the waterproof film as thin as possible.